Polarity Light is on.....

[Blue Nose]

I just bought a 1981 Bristol 32 and on the way home noticed that the polarity reversed light came on the electrical panel when trying to use shore power for the first time. It will not allow anything to run on shore power as is. I follwed the wire from the plug connector to the panel and it appeared that it was connected properly. The battery power system works fine but no shore power.

Any ideas or things I can try? All help is appreciated.

 

[Ross]

Check the outlet at the dock.

 

[Roger Long]

You need one of these for the first check:

The round part comes from a marine store. The square part with the LED's can be gotten from any hardware store. Check the marina outlet first. You can then use the dongle to check on your boat. I've heard that they don't give correct readings on some boats due to galvanic isolators and other boat specific wiring but I've never encountered that and it should work on a boat as simple as yours.

The round adapter is useful when you want to plug an extension cord in without running power through your boat's system, such as when drilling holes close to 110 volt wiring. Also, the only outlet available in the boatyard during the busy spring fitting out season may be the shorepower connector on the outlet rack.

 

[Old Skool Neil]

I followed the wire from the plug connector to the panel and it appeared that it was connected properly.

Best you go over this with a fine toothed comb from one end to the other, dock system included. The color code should be white-green-black both on the boat and the dock and the colors should run true throughout both systems.

Green = ground (not intended to carry current)
White = neutral (grounded but current carrying)
Black = hot

The plug and receptacle terminals that have the right angle tab are the grounds, the wider of the 2 remaining terminals are the neutrals. Further, neutral terminals are usually identified by a silver screw as opposed to brass for the hot.

Something's crossed and it could be in the boat, dock cord (only if someone's changed or "repaired" a plug end), the dock system or a combination. I would start at the dock receptacle and test for voltage between the hot and neutral, then the hot and ground. You should read 120 volts on both tests. If you don't, resolve this before proceeding which may mean calling the marina office for liability reasons. Once resolved, plug in the cord and perform the same tests at the female end of the dock cord looking for the same results. Successful tests mean the problem is in the boat - "Guaranteed".

For the safest system you should be ground fault protected as well. Post back if you want further detail. Hope this helps.

 

[Snotter]

Nigel Calder's book "Mechanical and Electrical Systems" has a good 1/2 chapter or so on ac wiring and using a digital meter for tracking down ground faults and reverse polarity issues.

As a side note, I've had my current boat for about 2.5 years. I just installed a galvanic isolator with an monitor a couple of weeks ago. As soon as I turned it on it indicated a ground fault and reversed polarity. It turned out that the previous owner wired what was supposed to be the hot wire to the ground lug on the back side of the shore cable receptical. Ignorance is bliss!

 

[sailingdog]

FYI, I'd point out that Blue Nose—using the name MobjackB32, got all the above advice and more on Sailnet, where he posted this exact same question a day ago, along with the names of electricians who could be hired to at least examine/inspect his system.

It doesn't appear that he's interested in hiring someone to inspect the shorepower system, even though it appears that the wiring was a real hack job—as the neutral and ground are connected on his boat's AC system, which is a really bad idea on a boat.

 

[Ross]

There is a time for questions and a time to get off your butt and get to work. I don't think we can help from a remote location. This will take work or money his choice.

 

[sailingdog]

Check the outlet at the dock.

While he hasn't checked the dock shore power posts, he has had this issue with two different cords at two different marinas, making the only thing common to both the boat.

We tried two different shore power cords at two different marinas and had the same problem. Makes me thing the problem is somewhere in the boat.

 

[Ross]

While he hasn't checked the dock shore power posts, he has had this issue with two different cords at two different marinas, making the only thing common to both the boat.

Time for him to learn to do his own troubleshooting or get out his checkbook..
If you plug a droplight into an outlet and it works but your power saw doesn't you don't blame the outlet.

 

[Blue Nose]

Neil,

Thank you for the helpful information. As SailingDog pointed out, I have posted on Sailnet and have received some advice. Since My boat is kept 1.5 hours away I want to gather as much information as possible so I can make the most of my time when I am at the boat focusing on the problem. At this point I am not ready to take my boat to an electrician until I know I can't solve the problem.

As indicated above, I feel certain the problem lies within the boat. We have even taken the Shore power receptical on the boat apart and inspected the wiring as decribed above. The only thing that I know has been changed in the past year are the batteries. Could be the PO did something to goof things up but she was very dependent on her boatyard for mechanical work. Since she was a day sailor the problem could date back to the owner before her which would be about 12 years.

I appreciate the good ideas and advice and hope to continue receiving more before I go back and start troubleshooting. To me it is like reading up on something before you dive in. I have had good success wiring house renovations, appliances, etc over the years so I do have some experience with electrical systems although I am no expert.

Looking forwardt o more good ideas and thoughts.

Thanks

 

[Old Skool Neil]

This isn't rocket science but be careful, it can be dangerous - even deadly. Remember the old mantra, "When in doubt - DON'T!!"

 

[Ross]

Disconnect from shore power and take apart every outlet and junction and inspect it for correctness. I have earned my living repairing houses for more than 30 years and I still occasionally screw up and have to go back and find out what I did wrong.

 

[Stu Jackson]

Understand your concern with the boat being far away. The real thing you NEED to do is to draw a wiring diagram. I also have never heard of a system where if the reverse polarity light came on nothing worked. If so, you have other issues. Calder's discussion is quite good and highly recommended. Then, of course, some people have RP lights like this, where two light come on when things are good and two different lights when things are wrong. We had one of our skippers who "missed" the normal and reverse writing...

And it's not two neutrals and a ground, it's black (hot), white (netural) and green (ground).

 

[Blue Nose]

I plan to go methodically and carefully. If a recepticle in the boat is cross wired for some reason, would that cause the polarity light to come on? I would think that would just trip the breaker assigned to it. Does the polarity sensor overide the panel? Meaning if the sensor detects a reverse polarity it prevents the panel from being able to be energized?

 

[Stu Jackson]

I plan to go methodically and carefully. If a recepticle in the boat is cross wired for some reason, would that cause the polarity light to come on? I would think that would just trip the breaker assigned to it. Does the polarity sensor overide the panel? Meaning if the sensor detects a reverse polarity it prevents the panel from being able to be energized?

Nope. It ONLY checks the INCOMING shorepower. Please: do some research, like reading a book about this stuff, which is a much more easily understood resource than we can provide. If that doesn't suit you, try a Google search. Try wikipedia. Really, there's been tons written about this that you should be able to find.

 

[Blue Nose]

and you can ask in forums so you can hear from those who have done it and wish to share their knowledge. That is one of the main purposes of a board like this. Thanks

 

[Old Skool Neil]

and you can ask in forums so you can hear from those who have done it and wish to share their knowledge.

I think we can all agree that we've read some excellent advice in this environment but we've also seen advice that was so wrong it was comical or perhaps more accurately, criminal. I see Nigel Calder's book mentioned daily as an excellent reference for all [boat] things electrical on this and other forums. You couldn't go wrong studying it.

 

[Benny]

Yes it seems like you have more problems than just a reverse polarity light. The fact that nothing works gives me the impression that your main AC breaker is tripped or defective. Hard to diagnose remotely. If working safely with electricity is beyond your abilities I do urge you to get an electrician.

 

[KD3PC]

yeah, Wikipaedia, that is the oracle to believe....NOT!

Find a reputable book or forum, then do some thinking yourself. And be careful as the voltages you are testing are fatal.

Yes I AM a licensed VA electrician.

dave

 

[Snotter]

FYI, I'd point out that Blue Nose—using the name MobjackB32, got all the above advice and more on Sailnet, where he posted this exact same question a day ago, along with the names of electricians who could be hired to at least examine/inspect his system.

It doesn't appear that he's interested in hiring someone to inspect the shorepower system, even though it appears that the wiring was a real hack job—as the neutral and ground are connected on his boat's AC system, which is a really bad idea on a boat.

I thought that the common practice IS to connect the ac and dc grounds, PROVIDED you are using a galvanic isolator OR an isolation transformer. Every boat connected to shore power should have some isolation device in my humble opinion.